1. Field of the Invention
The present invention pertains to an improved method of assembling a fault limiter, and, more particularly, to a method of assembling a one-piece fault limiter which permits the desirable compression of the arc quenching material therein.
2. Description of the Prior Art
The prior art discloses the use of a rigid resin body to contain a fault limiter wherein the space between the fusible element and the rigid resin body is filled with a particulate arc quenching medium, as shown in pending U.S. patent application Ser. No. 817,985--Biller, filed July 22, 1977 now U.S. Pat. No. 4,135,174 issued Jan. 16, 1979 and assigned to the same assignee as the present invention, and U.S. Pat. No. 4,012,708--Goe, Jr. The prior art also recognizes the need to keep the arc quenching particles immobile, particularly in high voltage applications, as shown in U.S. Pat. No. 3,838,375--Frind, et al.
In order to confine particulate arc quenching materials around the fusible element, the prior art suggests mixing the particulate with some form of binder, thereby creating a rigid subassembly. Such a method is shown in U.S. Pat. No. 3,838,375--Frind, et al, and U.S. Pat. No. 3,166,656--Hollmann, et al. The introduction of the binder around the fusible element can impair the function of the arc quenching material since the high temperatures associated with the triggering of the fuse may cause the binder to break down. Since no binder is required in the present invention, this problem is overcome.
An alternative way to minimize shifting of the particulate arc quenching medium is to fill a premolded open-ended insulating housing therewith and to then vibrate or tap the housing after it is filled to help the arc quenching material to settle, as shown in U.S. Pat. No. 3,866,318--Kozacka. However, this method does not permit the use of a one piece insulator, and therefore reduces the structural integrity of the fault limiter, since a separate insulating cover must be attached to the pre molded housing after the housing is filled with the arc quenching material.
The present invention overcomes these obstacles since the arc quenching material is positioned around the fusible element prior to molding a one piece resin insulator around the internal portion of the device. In addition, the present invention accomplishes the desired ends of providing an immobile and compact arc quenching medium by permitting the shrinking action of the resin insulator to act directly on the arc quenching material as it cures by providing a flexible barrier to contain the arc quenching material while the insulator is molded around it.